In recent years, one effective way to realize energy and space saving of refrigerators is to improve the heat insulating performance of refrigerators. As one method for improving the heat insulating performance of refrigerators, it is proposed to utilize vacuum heat insulating materials having high heat insulating performance. Since demands for energy saving are particularly increasing nowadays, it is the urgent need to improve the heat insulating performance of refrigerators by suitably utilizing and making the most of vacuum heat insulating materials whose heat insulating performance is several to ten times as great as the heat insulating performance of rigid urethane foam.
Conventional refrigerators including vacuum heat insulating materials are disclosed in Patent Literatures 1 to 4, for example. FIG. 25 is a front cross-sectional view of a refrigerator disclosed in Patent Literature 1. The refrigerator includes a box-shaped refrigerator body 1 and a door (not shown) for opening and closing a front opening of the refrigerator body 1. The refrigerator body 1 includes heat insulating walls. The heat insulating walls are formed by arranging a plurality of vacuum heat insulating materials (vacuum heat insulating panels) 39 and 40 in space formed between a composite resin inner casing 25 and a steel plate outer casing 24 surrounding the inner casing 25, and filling the space with rigid urethane foam (urethane foam resin) 26.
Among the heat insulating walls, the thickness of both side walls is such that the thickness of thinner portions (i.e., both side walls of storage compartments 2 and 6 whose temperature is relatively high) is approximately 30 mm, and the thickness of thicker portions (i.e., both side walls of a storage compartment 14 whose temperature is relatively low) is approximately 50 mm.
The plurality of vacuum heat insulating materials 39 and 40 include: vacuum heat insulating materials 39 disposed in close contact with faces of the outer casing; and a vacuum heat insulating material 40 disposed in close contact with faces of the inner casing. Each of the vacuum heat insulating materials 39 and 40 is formed to have a thickness of approximately 10 mm. The vacuum heat insulating materials 39 are flat plate-shaped, and are disposed at the outer casing side in a manner to extend to the vicinity of outer casing corners 41 at the left and right ends of the bottom surface. The vacuum heat insulating material 40 is provided so as to cover inner casing corners connected to the bottom surface of the inner casing 25, the inner casing corners facing the outer casing corners 41. Further, the vacuum heat insulating material 40 is disposed in a manner to extend along the faces of the inner casing, such that the vacuum heat insulating material 40 overlaps the vacuum heat insulating materials 39 when seen in the thickness direction of the side walls.